1. Field of the Invention
The present invention generally relates to code division multiple access (CDMA) technology, and especially relates to a code division multiple access communication system, and a base station control device and a base station thereof.
2. Description of the Related Art
In a code division multiple access radio communications system, communications are performed by assigning a code that is unique to each of a plurality of subscribers, and assigning the same wide range frequency band to the subscribers at the same time. For a specified communication through a channel, all other ongoing communications provided through other channels constitute an interference signal, whether the channels are in a cell to which the specified communication is being performed, or in other cells. Moreover, the power of a base station defines the number of subscribers that can be accommodated in the base station (or a sector), and the range of a service area of the base station. Therefore, transmission power and a target level of received power should be controlled such that there are no excesses or deficiencies. That is, the power levels should be controlled such that a desired signal to noise ratio (S/N) and a desired frame error rate (FER) are achieved. If optimal control is performed, the number of subscribers that can be accommodated in the entire communication system will be maximized. In a conventional communication system, a maintenance terminal for managing two or more base stations and base station control devices are used to predict and determine various parameters about the power of the base station, and control the base station, such that the maximum subscriber accommodation of the communication system is attained. The conventional communication system as mentioned above may provide optimal control, when the cell environment for communications, such as the number of subscribers, the number of base stations, and others, is relatively static, with few changes.
However, in actual operations, the cell environment dynamically changes according to various factors such as change of the number of subscribers, spatial deviation of the subscribers, temporal deviation of traffic from day to night, addition and deletion of the base stations, and change of a neighboring building. In order to optimally perform the power control of each base station, a quick response to the changes of the cell environment is required. By the conventional technique, if the cell environment changes, the maintenance terminal that manages the base station etc. needs to analyze and perform simulation such that parameters of the base stations etc. are reconfigured, which consumes time. When the cell environment changes rapidly, the parameters that are predicted as above may no longer be optimal.